Application of Spectrophotometer in platinum cobalt chroma measurement

Measurement of platinum cobalt chroma

Textile, printing and dyeing, petroleum, battery and other chemical industries often produce a lot of industrial wastewater in the production process. The national standard for detecting the chroma of wastewater mainly adopts platinum cobalt colorimetry and dilution multiple method.

The chroma of platinum and cobalt is expressed in Hazen unit, and the chroma of platinum and cobalt hexahydrate solution containing 1 mg of platinum (based on chloroplatinic acid) and 2 mg of cobalt chloride hexahydrate per liter of solution is 1 unit. Generally, the value range is 1-500. It is suitable for determining the color of transparent or slightly close to the reference platinum cobalt color number of liquid chemical products. This color feature is usually brown yellow.

20210721221540 17298 - Application of Spectrophotometer in platinum cobalt chroma measurement

Figure 1: platinum cobalt colorimetric standard solution

Three disadvantages of platinum cobalt colorimetry

The preparation process of standard colorimetric solution is complex

First, prepare standard colorimetric mother liquor, dissolve 1.00G cobalt chloride hexahydrate (CoCl2 · 6H2O) and 1.05g chloroplatinic acid or 1.25g potassium chloroplatinic acid in water in a 1000ml volumetric flask, add 100ml hydrochloric acid solution, dilute to the scale, and mix evenly. In 10 500ml volumetric flasks and 14 250ml volumetric flasks, add the body count of standard colorimetric mother liquor as shown below, dilute to the marking line with distilled water and mix.

20210721221959 77907 - Application of Spectrophotometer in platinum cobalt chroma measurement

Figure 2: preparation of platinum cobalt standard colorimetric solution

The storage of solution is difficult

The prepared solution should be put into a brown glass bottle with stopper and placed in a dark place. The mother solution can be stored for 1 year, and the diluted solution can be stored for 1 month. The solution often needs to be reconstituted, which is very troublesome.

Limitations of human eye colorimetry

Platinum cobalt colorimetry is based on the judgment of human eyes. The color is affected by environmental light source, observation angle and other factors. There are some differences in the actual visual colorimetry.

Spectrophotometer for measuring platinum and cobalt chroma

In view of the shortcomings of platinum cobalt colorimetry in the actual comparison of color, we can also use spectrophotometer to compare the solution color. There are three advantages of spectrophotometer

  1. There is no need to configure the solution, no need to consider the problem of material storage;
  2. The instrument is easy to operate and can measure directly;
  3. Platinum and cobalt data at a glance.

This paper introduces the measurement process with the desktop spectrophotometer CS-820N. First, adjust the measurement mode of the instrument to liquid chroma measurement. In this measurement mode, the chroma indexes of platinum, cobalt, Gardner, Cyberport and ASTM can be measured.
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Figure 3: select [liquid chroma] for measurement
After calibration according to the prompts, place the solution to be measured at the transmission measurement port, as shown in Figure 4 below.
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Figure 4: transmission measurement port
When measuring the solution, the instrument can directly feed back the platinum and cobalt value of the solution. As can be seen in Figure 5, the platinum and cobalt chroma value of the solution is 121.85. Through the value, the platinum and cobalt value of the solution can be intuitively known, which is convenient for subsequent work.
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Figure 5: measurement solution
In addition to water quality analysis, platinum cobalt chroma can also be used to measure the chroma of chemical and petrochemical products, such as glycerin, solvent, plasticizer, carbon tetrachloride, petroleum alcohol, etc. The table spectrophotometer CS-820N can be used to measure the above solutions.
bench top spectrophotometer cs 820n - Application of Spectrophotometer in platinum cobalt chroma measurement

Technical Data of Bench top Spectrophotometer CS-820N

Illumination/ Viewing System

Reflection: d/8(Diffused illumination, 8 degree viewing)

Simultaneous measurement of SCI/SCE (ISO7724/1, CIE No.15, ASTM E1164, ASTM-D1003-07, DIN5033 Teil7,JIS Z8722 Condition C standard)

Transmittance d/0(Diffused illumination, 0 degree viewing )


Silicon Photodiode Array

Grating Method

Concave Grating

Sphere Diameter




Wavelength Pitch


Half Band Width


Reflectance Range




Light Source

Pulse Xenon Lamp and LED

UV Measurement

Include UV, 400nm cut, 420nm cut, 460nm cut

Measurement Time

SCI/SCE < 2s

SCI+SCE < 4s

Measurement Aperture

Reflectance: XLAV Φ30mm, LAV 18mm,MAV Φ11mm,SAV Φ6mm


(Auto aperture size recognition)

Transmittance Sample Size

No limit on sample width and height, thickness 50mm


XLAV Spectrum Reflectance/Transmittance: standard deviation within 0.1%

XLAV Chromaticity value: Standard deviation within ΔE*ab 0.015 * When a white calibration plate is measured 30 x at 5-second intervals after white calibration

Inter-Instrument Agreement

XLAV ΔE*ab 0.15 (BCRA Series II, Average measurement of 12 tiles, at 23)





English, Russian, Spanish, Portuguese, Japanese, Thai, Korean, German, French, Polish, Chinese (simple and traditional),


Reflectance and Transmittance graph/value, color value, color difference values, pass/fail, color simulation, color assessment, haze, liquid chromaticity values, color tendency

Viewing Angles

2° and 10°

Color Spaces

L*a*b, L*C*h, Hunter Lab, Yxy, XYZ

Other Indices

WI(ASTM E313-00,ASTM E313-73,CIE/ISO, AATCC, Hunter, Taube Berger, Stensby)

YI(ASTM D1925,ASTM E313-00,ASTM E313-73),Tint(ASTM E313-00),Metamerism index milm, stain fastness, color fastness, ISO brightness, R457, A density, T density, E density, M Density, APHA/Pt-Co/Hazen, Gardner, Saybolt, ASTM color, Haze, Total Transmittance, Opacity, Color Strength

Color Difference

ΔE*ab, ΔE*CH, ΔE*uv, ΔE*cmc, ΔE*94, ΔE*00, ΔE*ab(hunter),555 shade sort

Storage Memory

8 GB U Disk for data storage and transfer

Screen Size

7 Inches Touch Screen



Operate Temperature

5-40(40-104F), relative humidity 80% (at 35) no condensation

Storage Temperature

-20-45(-4-113F), relative humidity 80% (at 35) no condensation


Power Adaptor, USB Cable, fixture for transmittance, U disk (PC software), Black Calibration Cavity, White and Green Calibration Tile,0% Calibration Tile (transmittance), Reflectance Test Support,30mm,18mm,11mm and 6mm apertures, reflectance sample fixture, Glass Cell 40x10mm

Optional Accessories

Heating Fixture for Transmittance, Vertical Support and Pneumatic ram for downward measurement, Reflectance fixture for small size sample, Reflectance Glass Cell Support, Corrosion-Resistant Protective Plate (non-removable), Sample Holder for Fiber, Film Fixture, Transmittance Fixture for Small Aperture, Trolley Case, European Standard Plug, American Standard Plug


USB, USB-B and RS-232

Instrument Size




Other Functions

1. Camera to view measurement area;

2. Support horizontal, vertical and downward measurement method (need optional accessories to support for downward measurement);

3. Auto humidity and temperature compensation function.

Source: China Tabletop Spectrophotometer Manufacturer offers Bench-top Spectrophotometer. 

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